CN111328056A

CN111328056A - Communication method and system for carrying out protocol adaptation based on ATT and read-write instruction

Info

Publication number: CN111328056A
Application number: CN202010067516.3A
Authority: CN
Inventors: 钟代笛; 段小炼; 曹小英; 冯海玲
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-01-20
Filing date: 2020-01-20
Publication date: 2020-06-23
Anticipated expiration: 2040-01-20
Also published as: CN111328056B

Abstract

The invention belongs to the technical field of data communication, and particularly relates to a communication method and a system for protocol adaptation based on ATT and read-write instructions, wherein the communication method comprises an ATT connection establishment process, an ATT operation process and an ATT planned disconnection process.

Description

Communication method and system for carrying out protocol adaptation based on ATT and read-write instruction

Technical Field

The invention belongs to the technical field of data communication, and particularly relates to a communication method and a communication system for protocol adaptation based on ATT and read-write instructions.

Background

Among many short-distance communication technologies, bluetooth is one of the most widely used and popular technologies; the low-power Bluetooth reuses a plurality of modules of a classic Bluetooth protocol stack, defines a brand-new physical layer and a link layer, and simplifies the realization of the protocol stack; most health monitoring equipment and health application programs only need to transmit a small amount of data, so that the low-power-consumption Bluetooth has great potential in the fields of medical health, physical fitness, family entertainment, safety guarantee and the like;

the attribute protocol (ATT) is a standard in the Bluetooth Low Energy (BLE) technology standard system, characterized in that: the slave devices compliant with the standard provide the exchanged data in the format of an Attribute (Attribute) defined in the BLE standard when exchanging data with the master device. The master device following the standard can operate on the attribute provided by the slave device by the "write request", "write response", "read request", "read response", and "information search request" methods among the attribute operation methods defined in the ATT. The ATT is composed of an ATT data unit (ATT PDU) and an ATT data exchange procedure. The ATTPDU is a data message which is exchanged at an ATT layer and conforms to the message format defined by ATT, and the byte length of a Payload (Payload) part of the ATT PDU does not exceed the maximum Payload length of the ATT PDU. The transmission of the ATT PDUs is done by the underlying transport layer. The ATT data exchange process comprises an ATT connection establishment process, an ATT operation process and an ATT planned disconnection process. The ATT connection establishment process is a process that two communication parties establish communication connection between the two parties at a bottom layer transmission layer by using a broadcast event and a scanning event defined in BLE; the ATT planned disconnection process is a process that communication connection between two communication parties is disconnected between the two communication parties at the bottom layer transmission layer by using a 'termination connection event' defined in BLE;

the invention is based on a data communication method and a system which are based on '201910765383.4' and are adaptive depending on ATT and indication;

in an application scenario of healthy device interoperation, a master device may need to communicate with multiple slave devices respectively, because each slave device operates independently, when the master device interacts with the slave devices, the master device needs to manage interoperation between the devices under different business targets at the same time, and an internal timing sequence of the master device is difficult to control, so that management overhead is high. The invention adopts the message flow control principle based on request and response, so that the master device can fully master the interaction rhythm between the master device and the slave device, flexibly schedules communication resources according to the self running resource condition and the emergency degree of the currently processed task, arranges the communication sequence and avoids the condition that two communication parties simultaneously send application layer messages to the other party. Compared with other communication modes in the field, the method can reduce the complexity of message flow control, strengthen the order of the message flow and improve the controllability of the data exchange of the application layer; in addition, the overhead for the interactive process of the slave device management is reduced, and the technical implementation difficulty of a terminal manufacturer is lower.

Disclosure of Invention

The invention provides a communication method and a communication system for protocol adaptation based on ATT and read-write instructions, which are used for solving the problems that the master device in the existing health device interaction technology in the background art lacks the control capability on the interaction rhythm and the overhead pressure caused by the management of the interaction process of the slave device is solved.

The technical problem solved by the invention is realized by adopting the following technical scheme: before data exchange is carried out on a master device and a slave device, a communication party and a communication party respectively establish a data communication protocol stack level structure which sequentially comprises a bottom layer transmission layer, an attribute protocol ATT layer, a universal attribute specification protocol adaptation CPA layer, a data exchange protocol PHD layer and an application layer from bottom to top;

the ATT layer comprises an ATT data exchange method, and the ATT data exchange method comprises the following steps:

the ATT establishes a connection process: the process that the two communication parties use the broadcast event and the scanning event defined in the BLE to establish communication connection between the two communication parties at a bottom layer transmission layer;

the ATT operation process comprises the following steps: in both communication sides, the CPA layer of the sender encapsulates the APDU transmitted by the PHD layer into CPA PDU, the CPA layer of the receiver de-encapsulates the CPA PDU received from the ATT layer into APDU, the CPA PDU is placed in the payload of the ATT PDU, and the data exchange process is completed by an attribute operation method based on the message flow control principle of request and response;

ATT has a planned disconnection process:

the initiator of the two communication parties initiates the process of disconnecting the ATT layer connection, and the receiver of the initiator receives the process of disconnecting the ATT layer connection.

Further, the attribute operation method based on the message flow control principle of the request and the response comprises a write request attribute operation method;

the write request attribute operation method comprises the following steps:

ATT write request: the master equipment sends an ATT write request and sends CPA PDU to the slave equipment;

and;

ATT write response: the slave receives the ATT write request to receive the CPA PDU and replies a corresponding ATT write response to the master.

Further, the attribute operation method based on the message flow control principle of the request and the response comprises a read request attribute operation method;

the read request attribute operation method comprises the following steps:

ATT read request: the master equipment sends an ATT read request and invites the slave equipment to send a CPA PDU;

and;

ATT read response: the slave device sends a corresponding ATT read response and sends the CPA PDU to the master device.

Further, the message flow control principle of the request and response further includes:

and if the sender does not receive the corresponding response after sending the request, prohibiting sending other requests.

Further, the initiating party of the two communication parties initiates the process of disconnecting the ATT layer connection, and the receiving party of the initiating party receives the process of disconnecting the ATT layer connection, which includes:

one of the two communication parties is an initiator of the role of the equipment initiating the disconnection of the ATT layer connection event, and the other party is a receiver of the role of the equipment receiving the disconnection of the ATT layer connection event;

if the PHD layer is in a "connected" state and the CPA layer does not currently have APDUs that need to be transmitted, then:

when the master device continuously waits for a corresponding defined time interval and still does not receive APDUs of the PHD layer or the device where the slave device is located does not generate new data to be transmitted after a certain time, the initiator can send a semantic ATT layer connection internal instruction for disconnecting the ATT layer connection according to the requirement of the application layer, and simultaneously, data of a working state is stored;

after receiving an internal instruction for disconnecting the ATT layer connection, the ATT layer of the initiator calls a connection termination event defined in the BLE and disconnects the connection of the underlying transmission layer;

after the connection of the bottom transmission layer is disconnected, the ATT layers of the initiator and the receiver send event notifications with the semantics of the disconnection of the ATT layer to the respective CPA layers, and respectively store working state data.

Further, either the master or slave device may act as, but not act as, an initiator or a recipient at the same time.

Further, the CPA PDU is composed of a header code and an information part code in sequence:

the header code comprises a CPA connection identification bit CLC with the length of 1 bit, if the CLC is set, the CPA connection is established, if the CLC is reset, the CPA layer is not connected, and the CLC is reset when the working state data is cleared.

Further:

the header code consists of four fields of a CPA connection identification bit CLC with the length of 1 bit, a length field expansion identification bit LE with the length of 1 bit, a message serial number ASN with the length of 6 bits and an APDU length AL in sequence;

if LE is 1, the AL field takes 3 bytes, and if LE is 0, the AL field takes 2 bytes.

Further, the information part encodes an APDU including only one PHD layer;

the ASN field and the AL field are unsigned integers, the initial value of the ASN field is 0 and the ASN field is reset to 0 when the working state data is cleared;

if the CPA layer is in the data exchange state, the ASN value increases with the increase of the number of the CPA PDUs transmitted or received, and the ASN value is increased by 2⁶Is a mold and can be recycled;

and;

if the LE bit is set, the byte length of the AL field is 3 bytes, and the maximum byte length of the APDU in the information part is 16MB at the moment;

if the LE bit is reset, the byte length of the AL field is 2 bytes, and the maximum byte length of the APDU in the information portion is 64KB at this time.

The invention also provides a communication system for protocol adaptation based on ATT and read-write instruction, wherein before the communication system exchanges data based on the master and slave devices, the two communication parties respectively establish a data communication protocol stack level structure which sequentially comprises a bottom layer transmission layer, an attribute protocol ATT layer, a universal attribute specification protocol adaptation CPA layer, a data exchange protocol PHD layer and an application layer from bottom to top;

the ATT layer comprises an ATT data exchange module, and the ATT data exchange module is used for:

implementing the ATT data exchange method of any of the above.

The beneficial technical effects are as follows:

the patent adopts the ATT layer to comprise an ATT data exchange method, and the ATT data exchange method comprises the following steps: the ATT establishes a connection process: the process that the two communication parties use the broadcast event and the scanning event defined in the BLE to establish communication connection between the two communication parties at a bottom layer transmission layer; the ATT operation process comprises the following steps: in both communication sides, the CPA layer of the sender encapsulates the APDU transmitted by the PHD layer into CPA PDU, the CPA layer of the receiver de-encapsulates the CPA PDU received from the ATT layer into APDU, the CPA PDU is arranged in the payload of the ATTPDU, and the data exchange process is completed through an attribute operation method based on the message flow control principle of request and response; ATT has a planned disconnection process: the initiator of the two communication parties initiates the process of disconnecting the ATT layer connection, and the receiver receives the process of disconnecting the ATT layer connection;

the exchanged data is provided in the format of the attributes defined in the BLE standard, and the master device following the standard can operate on the attributes provided by the slave device through the "write request", "write response", "read request", "read response", and "information search request" methods among the attribute operation methods defined in the ATT. The ATT is composed of ATT data units (ATT PDUs) and ATT data exchange procedures, the ATT PDUs are data messages exchanged at the ATT layer and conform to the ATT-defined message format, and the byte length of the Payload (Payload) part of the ATT PDUs does not exceed the "ATT PDU maximum Payload length". The transmission of the ATT PDUs is done by the underlying transport layer. The ATT data exchange process comprises an ATT connection establishment process, an ATT operation process and an ATT planned disconnection process. The ATT connection establishment process is a process that two communication parties establish communication connection between the two parties at a bottom layer transmission layer by using a broadcast event and a scanning event defined in BLE; the ATT planned disconnection process is a process that communication connection between two communication parties is disconnected between the two communication parties at the bottom layer transmission layer by using a 'termination connection event' defined in BLE;

through the constructed CPA layer, the master device (gateway device) can send data to the slave device (personal health device) through a write request defined by ATT and receive data from the slave device through a read request defined by ATT, and according to the message flow control principle of the request and the response, the master device can fully master the interaction rhythm between the master device and the slave device, flexibly arrange the exchange of APDUs of the application layer according to the self runtime resource condition, and avoid the situation that two communication parties send messages of the application layer to the other party at the same time. The master device assumes more responsibility for managing the interaction sequence during the "master-slave" device interaction process, thereby also enabling the slave device to reduce the management overhead in this respect and reducing the complexity of the technical implementation.

In summary, the technical scheme provided by the invention is adapted to respective technical characteristics of the PHD layer and the ATT layer, can save computing resources and system power consumption, improve user experience, reduce cost, and simultaneously does not have negative influence on system security, not only can effectively utilize the low power consumption characteristic of BLE, but also can keep the interaction synchronization of both communication parties at the application layer. The invention has strong universality and compatibility due to various advantages.

Drawings

FIG. 1 is an architectural diagram of a data communications protocol stack for the communications method of the present invention;

FIG. 2 is a general flow chart of the communication method of the present invention;

fig. 3 is a detailed flowchart of the communication method of the present invention;

FIG. 4 is a flow chart of the ATT connection establishment procedure of the communication method of the present invention;

FIG. 5 is a flow chart of the ATT operation of the communication method of the present invention;

FIG. 6 is a flow chart of an ATT planned disconnect process of the communication method of the present invention;

the technical scheme provided by the invention has flexibility in implementation, and a preferable scheme can be provided for the technical effect to be achieved by the invention by setting part of parameters in the technical scheme and setting up a better application design related to the parameters, and the invention is further described by combining the accompanying drawings as follows:

the numbers in the figures represent the following:

1-a bottom layer transmission layer, 2-an ATT layer, 3-a CPA layer, 4-a PHD layer and 5-an application layer;

ST 101: ATT establishes connection process;

ST 102: an ATT operation process;

ST 103: ATT has a planned disconnection process;

ST 201: the process that the two communication parties use the broadcast event and the scanning event defined in the BLE to establish communication connection between the two communication parties at a bottom layer transmission layer;

ST 202: in both communication sides, a CPA layer of a sender encapsulates APDUs transmitted by a PHD layer into CPA PDUs;

ST 203: the CPA layer of the receiving party decapsulates the CPA PDU received from the ATT layer into an APDU;

ST 204: CPA PDU is placed in payload of ATT PDU, and data exchange process is completed through attribute operation method based on message flow control principle of request and response;

ST 205: the initiator of the two communication parties initiates the process of disconnecting the ATT layer connection, and the receiver receives the process of disconnecting the ATT layer connection;

the first embodiment is as follows:

in this embodiment: as shown in fig. 1, 2, and 3, a communication method for performing protocol adaptation based on ATT and read-write command includes that before data exchange is performed between a master device and a slave device, both sides of the communication respectively establish a data communication protocol stack level structure, which sequentially comprises a bottom layer transmission layer, an attribute protocol ATT layer, a generic attribute specification protocol adaptation CPA layer, a data exchange protocol PHD layer, and an application layer from bottom to top;

ATT establish connection procedure ST 101: a process ST201 in which the two communicating parties establish a communication connection between the two parties at the underlying transport layer using the broadcast event and the scan event defined in BLE;

ATT running process ST 102: in both communication parties, the CPA layer of the sender encapsulates the APDU transmitted by the PHD layer into CPAP PDU ST202, the CPA layer of the receiver de-encapsulates the CPA PDU received from the ATT layer into APDU ST203, the CPAP PDU is placed in the payload of the ATT PDU, and the data exchange process ST204 is completed through an attribute operation method based on the message flow control principle of request and response;

ATT planned disconnection procedure ST 103:

the initiator of the two communicating parties initiates the process of disconnecting the ATT layer connection, and the receiver thereof accepts the process of disconnecting the ATT layer connection ST 205.

The two communication parties provide the exchanged data according to the format of the attribute defined in the BLE standard, and the master device following the BLE standard can operate the attribute provided by the slave device through the methods of 'write request', 'write response', 'read request', 'read response' and 'information search request' in the attribute operation methods defined in the ATT. The ATT is composed of ATT data units (ATTPDUs) and ATT data exchange procedures, the ATT PDUs are data messages exchanged at the ATT layer and conform to the ATT-defined message format, and the byte length of the Payload (Payload) part of the ATT PDUs does not exceed the "ATT PDU maximum Payload length". The transmission of the ATT PDUs is done by the underlying transport layer. The ATT data exchange process comprises an ATT connection establishment process, an ATT operation process and an ATT planned disconnection process. The ATT connection establishment process is a process that two communication parties establish communication connection between the two parties at a bottom layer transmission layer by using a broadcast event and a scanning event defined in BLE; the ATT planned disconnection process is a process that communication connection between two communication parties is disconnected between the two communication parties at the bottom layer transmission layer by using a 'termination connection event' defined in BLE;

since the slave CPA layer and the master CPA layer in this embodiment transmit and receive CPAPDU based on ATT. CPAP PDU is put in the payload of ATT PDU, and both communication sides complete the exchange of CPAP PDU by transmitting and receiving ATT PDU. In this embodiment, attribute operation methods of "write request", "write response", "read request", "read response", and "information search request" defined by the ATT are used to implement a data exchange process between the slave device CPA layer and the master device CPA layer. More specifically, the master CPA layer sends CPA PDUs to the slave CPA layer through a "write request" defined by the ATT. The master CPA layer invites the slave CPA layer to send CPA PDU through a read request defined by the ATT, and then the slave CPA layer sends CPA PDU to the master CPA layer through a read response defined by the ATT. The ATT defines a "request-response" message flow control principle, that is, after a "request" (write request or read request) is sent, the master device does not send other requests until a corresponding response is not received.

In CPA, the sending or receiving of one CPA PDU is regarded as the minimum operation of the CPA layer, namely, the operation which is not subdivided and must be completed at one time, the master CPA layer sends one CPA PDU, and the master CPA layer does not send other CPA PDUs before the slave CPA layer confirms to completely receive the CPA PDU; the master CPA layer invites the slave CPA layer to send one CPA PDU and does not receive other CPA PDUs until the slave CPA layer completely sends the CPA PDU. The CPA specification mainly considers that, in general, if a CPA PDU cannot be completely placed in an ATT PDU of "write request" or "read response", the master CPA layer will send a group (read-through multiple pairs) "write request/write response" to complete the transmission of one CPA PDU or send a group (continuous multiple pairs) "read request/read response" to complete the transmission of one CPA PDU;

The attribute operation method based on the message flow control principle of the request and the response comprises a write request attribute operation method;

the write request attribute operation method comprises the following steps:

and;

The attribute operation method based on the message flow control principle of the request and the response comprises a read request attribute operation method;

the read request attribute operation method comprises the following steps:

and;

If the sender does not receive the corresponding response after sending the request, the sender is prohibited from sending other requests;

example two:

as shown in fig. 4, the ATT connection establishment procedure includes:

the slave equipment calls a broadcast event defined by BLE to send a broadcast packet through a broadcast channel;

the master device calls a scanning event defined by BLE to receive a broadcast packet;

the master device sends a connection request to the slave device;

and the master device and the slave device enter the ATT operation process and transmit an ATT layer connection established event notification to the respective CPA layer.

As shown in fig. 5, the ATT running process example described in fig. 5 is only used for describing the interactive process of data, and it cannot be guaranteed that the timing chart can be completely copied.

The ATT operation process can be summarized as follows:

when the master device sends data: the master equipment CPA layer issues a CPA PDU to the ATT layer, and further the master equipment ATT layer sends the CPA PDU as a payload to the slave equipment ATT layer through a write request; after receiving the write request, the ATT layer of the slave device transmits the payload part to the CPA layer of the slave device and replies corresponding write response. The CPA layer carries out subsequent operations, and judges whether the CPA PDU is complete or needs to be sent to an upper PHD layer or at which connection stage of the CPA layer the current CPA layer is in.

When the master device receives data: the method comprises the steps that a master device ATT layer sets and sends a reading request to a slave device ATT layer according to application layer requirements; after receiving the read request, the ATT layer of the slave device waits for the receiving of a CPA PDU from the CPA layer of the slave device and replies the CPA PDU to the ATT layer of the master device as a payload through a read response, the master device transmits the payload part to the CPA layer of the slave device after receiving the read response, and the CPA layer carries out subsequent operation.

In the ATT operation process, the execution sequence of the main equipment for sending and receiving data is designed by the application layer according to the requirements of the application layer and is triggered by the CPA layer. Essentially, the ATT layer does not parse the transmitted data, which in this patent can be understood as a data vehicle managed by the CPA layer.

As shown in fig. 6, the ATT planned disconnect process can be summarized as:

one of the two communication parties is an initiator of the device role initiating the disconnection of the ATT layer connection event, and the other party is a receiver of the device role receiving the disconnection event of the ATT layer connection.

the initiator can send a semantic ATT layer connection internal instruction for disconnecting the ATT layer to the ATT layer of the initiator according to the requirement of the application layer, and simultaneously, the data of the working state is stored;

after receiving an internal instruction for disconnecting the ATT layer connection, the ATT layer of the initiator calls a connection termination event defined in the BLE, namely, the two communication parties exit from the connection state and enter a broadcast state, a scanning state or a standby state (the state is determined according to the state before the ATT establishes the connection);

after the connection of the ATT layer is disconnected, the ATT layers of the initiator and the receiver send event notifications with the semantics of the disconnection of the ATT layer to the respective CPA layers, and respectively store working state data.

Either the master or slave device can act as an initiator or a receiver, but not both.

The working principle is as follows:

the invention includes an ATT data exchange method through the ATT layer, and the ATT data exchange method comprises the following steps: the ATT establishes a connection process: the process that the two communication parties use the broadcast event and the scanning event defined in the BLE to establish communication connection between the two communication parties at a bottom layer transmission layer; the ATT operation process comprises the following steps: in both communication sides, the CPA layer of the sender encapsulates the APDU transmitted by the PHD layer into CPA PDU, the CPA layer of the receiver de-encapsulates the CPA PDU received from the ATT layer into APDU, the CPA PDU is arranged in the payload of the ATTPDU, and the data exchange process is completed through an attribute operation method based on the message flow control principle of request and response; ATT has a planned disconnection process: the initiator of the two communication parties initiates the process of disconnecting the ATT layer connection, and the receiver receives the process of disconnecting the ATT layer connection;

since the slave CPA layer and the master CPA layer in this embodiment transmit and receive CPAPDU based on ATT. CPAP PDU is put in the payload of ATT PDU, and both communication sides complete the exchange of CPAP PDU by transmitting and receiving ATT PDU. In this embodiment, attribute operation methods of "write request", "write response", "read request", "read response", and "information search request" defined by the ATT are used to implement a data exchange process between the slave device CPA layer and the master device CPA layer. More specifically, the master CPA layer sends CPA PDUs to the slave CPA layer through a "write request" defined by the ATT. The master CPA layer invites the slave CPA layer to send CPAP PDU through the read request defined by the ATT, and then the slave CPA layer sends CPAP PDU to the master CPA layer through the read response defined by the ATT. The ATT defines a "request-response" message flow control principle, that is, after a "request" (write request or read request) is sent, the master CPA layer does not send other requests until a corresponding response is not received. In CPA, the sending or receiving of one CPA PDU is regarded as the minimum operation of the CPA layer, namely, the operation which is not subdivided and must be completed at one time, the master CPA layer sends one CPA PDU, and the master CPA layer does not send other CPA PDUs before the slave CPA layer confirms to completely receive the CPA PDU; the master CPA layer invites the slave CPA layer to send one CPA PDU and does not receive other CPA PDUs until the slave CPA layer completely sends the CPA PDU. The CPA specification mainly considers that, in general, if a CPA PDU cannot be completely placed in an ATT PDU of "write request" or "read response", the master CPA layer will send a group (read-through multiple pairs) "write request/write response" to complete the transmission of one CPA PDU or send a group (continuous multiple pairs) "read request/read response" to complete the transmission of one CPA PDU.

The invention solves the problem that the master device in the existing health device interaction technology lacks the control capability on the interaction rhythm and the problem of overhead pressure caused by managing the interaction process of the slave device.

By the invention, the master device can fully master the interaction rhythm between the master and slave devices, flexibly arrange the exchange of the application layer APDU according to the self run-time resource condition, and avoid the condition that two communication parties simultaneously send the application layer message to the other party. The master device assumes more responsibility for managing the interaction sequence during the "master-slave" device interaction process, thereby also enabling the slave device to reduce the management overhead in this respect and reducing the complexity of the technical implementation.

In summary, the technical scheme provided by the present invention is adapted to respective technical characteristics of the PHD layer and the ATT layer, and has the technical effects of saving computing resources and system power consumption, improving user experience, reducing cost, and simultaneously not causing negative impact on system security, not only effectively utilizing the low power consumption characteristic of BLE, but also keeping synchronization of interaction of both communication parties at the application layer. The invention has strong universality and compatibility due to various advantages.

The technical solutions of the present invention or similar technical solutions designed by those skilled in the art based on the teachings of the technical solutions of the present invention are all within the scope of the present invention to achieve the above technical effects.

Claims

1. The communication method is characterized in that before data exchange is carried out on a master device and a slave device, a communication party and a communication party respectively establish a data communication protocol stack level structure which sequentially comprises a bottom layer transmission layer, an attribute protocol ATT layer, a universal attribute specification protocol adaptation CPA layer, a data exchange protocol PHD layer and an application layer from bottom to top;

ATT has a planned disconnection process:

2. The communication method according to claim 1, wherein the attribute operation method based on the message flow control principle of request and response comprises a write request attribute operation method;

the write request attribute operation method comprises the following steps:

and;

3. The communication method according to claim 2, wherein the attribute operation method based on the message flow control principle of request and response comprises a read request attribute operation method;

the read request attribute operation method comprises the following steps:

and;

4. The communication method according to claim 1, wherein the message flow control principle of the request and response further comprises:

5. The communication method according to claim 1, wherein the initiating party of the two communicating parties initiates the process of disconnecting the ATT layer connection, and the accepting of the accepting by the receiving party of the initiating party of the two communicating parties comprises:

when the master device continuously waits for a corresponding defined time interval and still does not receive APDU of the PHD layer or the device where the slave device is located does not generate new data to be transmitted after a certain time, the initiator can send a semantic ATT layer connection internal instruction for disconnecting the ATT layer through the CPA layer and simultaneously save data of a working state;

6. The communication method according to claim 5, wherein either the master device or the slave device can act as the initiator or the recipient, but not simultaneously.

7. The communication method according to claim 1, wherein the CPA PDU is composed of a header code and an information part code in sequence:

8. The communication method according to claim 7,

9. The communication method according to claim 8, wherein the information part codes APDUs including only one PHD layer;

and;

10. The communication system is characterized in that before the communication system exchanges data based on master and slave equipment, both communication sides respectively establish a data communication protocol stack level structure which sequentially comprises a bottom layer transmission layer, an attribute protocol ATT layer, a universal attribute specification protocol adaptation CPA layer, a data exchange protocol PHD layer and an application layer from bottom to top;

implementing the ATT data exchange method according to any one of claims 1 to 9.